1. Field of the Invention
The present invention relates to a viewing apparatus which includes a viewing optical system (e.g., a viewing optical system of a telescope or a binocular) and a photographing optical system for photographing an object viewed through the viewing optical system, wherein a distant object can be viewed through the viewing optical system, and recorded as image data at the same time.
2. Description of the Prior Art
Telescopes and binoculars are known as viewing apparatuses for viewing distant objects. However, such conventional viewing apparatuses do not have a function of recording object images which are viewed therethrough. Although there have been various proposals of combining a viewing apparatus such as a telescope or a binocular with a camera to achieve such an image recording function, none of these proposals are practical for ordinary users due to, for example, an unavoidable increase in size of the viewing apparatus.
The ideal magnification of a binocular for general use is approximately seven times (xc3x977). This degree of magnification is advantageous for viewing a distant object closely with a decreased influence in hand shake. Nevertheless, the field of view of a binocular corresponds to that viewed through a long-focus telephoto lens system of over 300 mm attached to a 35 mm camera. Accordingly, if the function of recording an image viewed through a binocular is achieved simply by combining a typical binocular with a conventional camera, the system becomes bulky.
In addition, the photographing lens system of such a multi-function viewing apparatus is required to have a high optical performance if high-resolution object images are to be recorded. This inevitably increases the number of lens elements to thereby increase the cost of production and the weight of the entire optical system.
In such a multi-function viewing apparatus, to maintain adequate operability as a viewing apparatus, it is desirable for the focusing mechanism of the photographing optical system to operate in association with the focusing operation of the binocular. However, in a long-focus telephoto lens system such as the aforementioned long-focus telephoto lens system having a focal length of over 300 mm, it is impossible to achieve a focusing operation with a sufficient degree of accuracy simply by the focusing mechanism of the photographing optical system operating in association with the focusing operation of the binocular since such a long-focus telephoto lens system is required to be focused on viewing objects with a high degree of accuracy.
In a focusing operation of a viewing apparatus, it is normally the case that a user visually finds a sharp focal point on an object image while manually operating the apparatus. However, vision varies greatly between individuals, and accordingly, the focal point varies greatly between individuals.
The present invention provides a viewing optical system having both a distant-object viewing function and a distant-object image recording function with a low cost of production without increasing the size of the optical system, and further provides such a viewing optical system which achieves easy operability in a focusing operation.
As an aspect of the invention, a viewing apparatus having a photographing function is provided, including a viewing system having a viewing optical system, the viewing optical system having a positive objective optical system and an eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the eyepiece optical system; and a photographing system including a photographing optical system for photographing the object viewed through the eyepiece optical system, the photographing optical system being provided independently of the viewing optical system. The photographing optical system includes a first lens group and a second lens group. The photographing system includes two focusing mechanisms, which operate independently from each other, for changing both absolute positions of the first lens group and the second lens group and a relative position of the first lens group and the second lens group on an optical axis of the photographing optical system.
It is desirable for the first lens group and the second lens group to be arranged in that order from an object, the two focusing mechanisms moving the first lens group and the second lens group along the optical axis independent of each other to shift an image of the object to a predetermined point. It is also desirable for the following conditions (1) and (2) to be satisfied:
0.1 less than ft/f0 less than 0.7xe2x80x83xe2x80x83. . . (1)
0.4 less than |TI/TII| less than 2.5xe2x80x83xe2x80x83. . . (2)
wherein
xe2x80x9cftxe2x80x9d represents the focal length of the photographing optical system,
xe2x80x9cf0xe2x80x9d represents the focal length of the positive objective optical system of the viewing optical system,
xe2x80x9cTrxe2x80x9d represents the traveling distance of the first lens group necessary for achieving focus from an infinite distance to a finite object distance, and
xe2x80x9cTIIxe2x80x9d represents the traveling distance of the second lens group necessary for achieving focus from an infinite distance to the finite object distance.
It is desirable for the eyepiece optical system to have a positive power, wherein the following condition (3) is satisfied:
5 less than f0/fexe2x80x83xe2x80x83. . . (3)
wherein
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system, and
xe2x80x9cfexe2x80x9d represents the focal length of the eyepiece optical system of the viewing optical system.
The reason why the viewing optical system can be prevented from increasing in size while satisfying conditions (1) through (3) (even though the focal length of the photographing optical system in particular is shortened) is that digital cameras using an image pick-up device (e.g., CCD) instead of conventional cameras using a silver-halide film have become popularized in recent years. The scale of integration of the CDD has increased rapidly; the size of the image plane (picture plane) of a typical CCD is approximately one tenth of the size of a conventional 35 mm film frame. Moreover, even if the focusing mechanism of the photographing optical system operates in association with the focusing mechanism of the viewing optical system, a sufficiently high focusing sensitivity can be obtained by making the focal length of the photographing lens system shorter than the focal length of the objective optical system of the viewing optical system. Furthermore, providing the viewing optical system with a focus system for independently moving the first and second lens groups along the optical axis to shift an image focal point of an image of a viewing object to a given point makes it possible to correct deviation of the focal point set by a manual operation of the user with an auxiliary device such as an autofocus system.
The viewing system can include a first focusing mechanism for moving at least one optical element of the viewing optical system along the optical axis to shift an object image formed by the photographing optical system to a given point to focus the viewing system on the object, a second focusing mechanism for moving one of the first lens group and the second lens group to shift an image formed by the photographing optical system, and an association mechanism which interconnects the first focusing mechanism with the second focusing mechanism to allow the first focusing mechanism to operate in association with the second focusing mechanism.
The viewing system can include a telescope, wherein the eyepiece optical system has positive power, and wherein an image formed through the positive objective optical system is viewed through the positive eyepiece optical system.
As another aspect of the invention, a viewing apparatus having a photographing function is provided, including a viewing system having a pair of viewing optical systems, each of the pair of viewing optical systems having a positive objective optical system and an eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the eyepiece optical system; and a photographing system including a photographing optical system for photographing the object image viewed through the eyepiece optical system, the photographing optical system being provided independent of the pair of viewing optical systems. The photographing optical system includes a first lens group and a second lens group. The photographing system includes two focusing mechanisms, which operate independently from each other, for changing both absolute positions of the first lens group and the second lens group and a relative position of the first lens group and the second lens group on an optical axis of the photographing optical system.
It is desirable for the optical axis of the photographing optical system to be provided between two optical axes of the pair of viewing optical systems Furthermore, the photographing system can include an image pick-up device, an object image being focused on the image pick-up device through the photographing optical system to be recorded as image data.
A Petzval lens system is known as an optical system used as a telephoto lens system. A Petzval lens system includes a positive first lens group and a positive second lens group, wherein each of the first and second lens groups is constituted by a positive lens element and a negative lens element. The Petzval lens system is often used as a telephoto lens system since a preferable optical performance is obtained with a relatively less number of optical elements.
Accordingly, it is desirable that the Petzval lens system serve as the photographing optical system. Namely, it is desirable for the photographing optical system to include a positive first lens group having a positive lens element and a negative lens element, and a positive second lens group having a positive lens element and a negative lens element, and wherein the following condition (4) is satisfied:
0.15 less than DI-II/f less than 0.7xe2x80x83xe2x80x83. . . (4)
wherein
xe2x80x9cDI-IIxe2x80x9d represents the space between the first lens group and the second lens groups when an object at infinity is in an in-focus state, and
xe2x80x9cfxe2x80x9d represents the focal length of the photographing optical system.
It is desirable for the following conditions (5) and (6) to be satisfied:
1 less than ACI/ACIIxe2x80x83xe2x80x83. . . (5)
20 less than xcexdIp/xcexdInxe2x80x83xe2x80x83. . . (6)
wherein
xe2x80x9cACIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|)in the first lens group,
xe2x80x9cACIIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|) in the second lens group,
xe2x80x9cxcexdIpxe2x80x9d represents Abbe number of the positive lens element of the first lens group, and
xe2x80x9cxcexdInxe2x80x9d represents Abbe number of the negative lens element of the first lens group.
The positive lens element of the first lens group and the negative lens element of the first lens group can be cemented to each other.
It is desirable for the first lens group and the second lens group to be arranged in that order from an object; wherein one of the two focusing mechanisms moves the photographing optical system along the optical axis, wherein the other of the two focusing mechanisms moves the first lens group independently, and the following conditions (7) and (8) are satisfied:
0.1 less than ft/f0 less than 0.7xe2x80x83xe2x80x83. . . (7)
0.2 less than |TA/TI| less than 1.5xe2x80x83xe2x80x83. . . (8)
wherein
xe2x80x9cftxe2x80x9d represents the focal length of the photographing optical system,
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system,
xe2x80x9cTAxe2x80x9d represents the traveling distance of the photographing optical system necessary for achieving focus from an infinite distance to a finite object distance, and
xe2x80x9cTIxe2x80x9d represents the traveling distance of the first lens group necessary for achieving focus from an infinite distance to the finite object distance.
It is desirable for the eyepiece optical system to have a positive power, and wherein the following condition (9) is satisfied:
5 less than f0/fexe2x80x83xe2x80x83. . . (9)
wherein
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system, and
xe2x80x9cfexe2x80x9d represents the focal length of the eyepiece optical system of the viewing optical system.
The viewing apparatus can include a first focusing mechanism for moving at least one optical element of the viewing optical system along the optical axis in accordance with a variation of an object distance to shift an image of the object image to a predetermined point to focus the viewing system on the object, a second focusing mechanism for moving one of the photographing optical system and the first lens group, and an association mechanism which interconnects the first focusing mechanism with the second focusing mechanism to allow the first focusing mechanism to operate in association with the second focusing mechanism.
The viewing system can include as a telescope, wherein the eyepiece optical system has a positive power, and wherein an image formed through the positive objective optical system is viewed through the positive eyepiece optical system.
As another aspect of the invention, a viewing apparatus having a photographing function is provided, including a viewing system having a pair of viewing optical systems, each of the pair of viewing optical systems having a positive objective optical system and an eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the eyepiece optical system, and a photographing system including a photographing optical system for photographing the object viewed through the eyepiece optical system, the photographing optical system being provided independently from the pair of viewing optical systems. The photographing optical system includes a first lens group and a second lens group, in that order from an object. The photographing system includes two focusing mechanisms which operate independently from each other. One of the two focusing mechanisms moves the photographing optical system along the optical axis, and the other of the two focusing mechanisms moves the first lens group along the optical axis independently. Furthermore, the following conditions (7) and (8) are satisfied:
xe2x80x830.1 less than ft/f0 less than 0.7xe2x80x83xe2x80x83. . . (7)
0.2 less than |TA/TI| less than 1.5xe2x80x83xe2x80x83. . . (8)
wherein
xe2x80x9cftxe2x80x9d represents the focal length of the photographing optical system,
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system,
xe2x80x9cTAxe2x80x9d represents the traveling distance of the photographing optical system necessary for achieving focus from an infinite distance to a finite object distance, and
xe2x80x9cTIxe2x80x9d represents the traveling distance of the first lens group necessary for achieving focus from an infinite distance to the finite object distance.
It is desirable for the optical axis of the photographing optical system to be provided between two optical axes of the pair of viewing optical systems.
Furthermore, the photographing system can include an image pick-up device, an object image being focused on the image pick-up device through the photographing optical system to be recorded as image data.
The photographing optical system can include a positive first lens group having a positive lens element and a negative lens element, and a positive second lens group having a positive lens element and a negative lens element, and wherein the following condition (10) is satisfied:
0.15 less than DI-II/f less than 0.7xe2x80x83xe2x80x83. . . (10)
wherein
xe2x80x9cDI-IIxe2x80x9d represents the space between the first lens group and the second lens groups when an object at infinity is in an in-focus state, and
xe2x80x9cfxe2x80x9d represents the focal length of the photographing optical system.
It is desirable for the following conditions (11) and (12) to be satisfied:
1 less than ACI/ACIIxe2x80x83xe2x80x83. . . (11)
20 less than xcexdIp/xcexdInxe2x80x83xe2x80x83. . . (12)
wherein
xe2x80x9cACIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|)in the first lens group,
xe2x80x9cACIIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|) in the second lens group,
xe2x80x9cxcexdIpxe2x80x9d represents Abbe number of the positive lens element of the first lens group, and
xe2x80x9cxcexdInxe2x80x9d represents Abbe number of the negative lens element of the first lens group.
The positive lens element of the first lens group and the negative lens element of the first lens group can be cemented to each other.
It is desirable for the first lens group and the second lens group to be arranged in that order from an object, wherein one of the two focusing mechanisms moves the photographing optical system along the optical axis, and the other of the two focusing mechanisms moves the second lens group along the optical axis independently. The following conditions (13) and (14) are satisfied:
0.1 less than ft/f0 less than 0.7xe2x80x83xe2x80x83. . . (13)
0.2 less than |TA/TII| less than 1.5xe2x80x83xe2x80x83. . . (14)
wherein
xe2x80x9cftxe2x80x9d represents the focal length of the photographing optical system,
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system,
xe2x80x9cTAxe2x80x9d represents the traveling distance of the photographing optical system necessary for achieving focus from an infinite distance to a finite object distance, and
xe2x80x9cTIIxe2x80x9d represents the traveling distance of the second lens group necessary for achieving focus from an infinite distance to the finite object distance.
The eyepiece optical system can have a positive power, wherein the following condition (15) is satisfied:
5 less than f0/fcxe2x80x83xe2x80x83. . . (15)
wherein
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system, and
xe2x80x9cfexe2x80x9d represents the focal length of the eyepiece optical system of the viewing optical system.
The viewing apparatus can include a first focusing mechanism for moving at least one optical element of the viewing optical system along the optical axis in accordance with a variation of an object distance to shift an image of the object to a given point; a second focusing mechanism for moving one of the photographing optical system and the second lens group; and an association mechanism which interconnects the first focusing mechanism with the second focusing mechanism to allow the first focusing mechanism to operate in association with the second focusing mechanism.
The viewing system can serve as a telescope, wherein the eyepiece optical system has a positive power, and wherein an image formed through the positive objective optical system is viewed through the positive eyepiece optical system.
As a further aspect of the invention, a viewing apparatus having a photographing function is provided, including a viewing system having a pair of viewing optical systems, each of the pair of viewing optical systems having a positive objective optical system and an eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the eyepiece optical system, and a photographing system including a photographing optical system for photographing the object image viewed through the eyepiece optical system, the photographing optical system being provided independently from the pair of viewing optical systems. The photographing optical system includes a first lens group and a second lens group in that order from the object. The photographing system includes two focusing mechanisms which operate independently from each other. One of the two focusing mechanisms moves the photographing optical system along the optical axis, and the other of the two focusing mechanisms moves the second lens group along the optical axis independently. The following conditions (13) and (14) are satisfied:
0.1 less than ft/f0 less than 0.7xe2x80x83xe2x80x83. . . (13)
0.2 less than |TA/TII| less than 1.5xe2x80x83xe2x80x83. . . (14)
wherein
xe2x80x9cftxe2x80x9d represents the focal length of the photographing optical system,
xe2x80x9cf0xe2x80x9d represents the focal length of the objective optical system of the viewing optical system,
xe2x80x9cTAxe2x80x9d represents the traveling distance of the photographing optical system necessary for achieving focus from an infinite distance to a finite object distance, and
xe2x80x9cTIIxe2x80x9d represents the traveling distance of the second lens group necessary for achieving focus from an infinite distance to the finite object distance.
It is desirable for the optical axis of the photographing optical system to be provided between two optical axes of the pair of viewing optical systems.
Furthermore, the photographing system can include an image pick-up device, an object image being focused on the image pick-up device through the photographing optical system to be recorded as image data.
The photographing optical system can include a positive first lens group including a positive lens element and a negative lens element, and a positive second lens group including a positive lens element and a negative lens element, and wherein the following condition (16) is satisfied:
0.15 less than DI-II/f less than 0.7xe2x80x83xe2x80x83. . . (16)
wherein
xe2x80x9cDI-IIxe2x80x9d represents the space between the first lens group and the second lens groups when an object at infinity is in an in-focus state, and
xe2x80x9cfxe2x80x9d represents the focal length of the photographing optical system.
It is desirable for the following conditions (17) and (18) to be satisfied:
1 less than ACI/ACIIxe2x80x83xe2x80x83. . . (17)
20 less than xcexdIp/xcexdInxe2x80x83xe2x80x83. . . (18)
wherein
xe2x80x9cACIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|)in the first lens group,
xe2x80x9cACIIxe2x80x9d represents the sum of the absolute values of the reciprocals of the products of the focal length of each lens element and Abbe numbers thereof (|1/(fi*xcexdi)|) in the second lens group,
xe2x80x9cxcexdIpxe2x80x9d represents Abbe number of the positive lens element of the first lens group, and
xe2x80x9cxcexdInxe2x80x9d represents Abbe number of the negative lens element of the first lens group.
The positive lens element of the first lens group and the negative lens element of the first lens group can be cemented to each other.
As a further aspect of the invention, a viewing apparatus is provided, including a binocular optical system including a pair of viewing optical systems, each of the pair of viewing optical systems having a positive objective optical system and an eyepiece optical system, an image of an object formed through the positive objective optical system being viewed through the eyepiece optical system, and a photographing system including a photographing optical system for photographing the object viewed through the eyepiece optical system, the photographing optical system being provided independently from the pair of viewing optical systems. The photographing optical system includes a first movable lens group and a second movable lens group. The photographing system can include two focusing mechanisms, which operate independently from each other, for changing both absolute positions of the first lens group and the second lens group and a relative position of the first lens group and the second lens group on an optical axis of the photographing optical system. One of the two focusing mechanisms is interconnected with, and operates in association with, a manual focusing mechanism of the binocular optical system, and the other of the two focusing mechanisms includes an autofocus system.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-301870 (filed on Sep. 28, 2001) which is expressly incorporated herein in its entirety.